Decommissioning aging nuclear reactors
“By managing and sharing this information, we’re protecting the knowledge and lessons learned for generations to come. We’re also helping build confidence and trust among the public and other key stakeholders by showing them that these facilities can be maintained safely and effectively throughout their entire life cycle.”
According to Boing, the process for safely decommissioning a facility generally proceeds in four key steps. These same steps apply for all different kinds of facilities, including research reactors, which are non-power reactors that typically provide neutrons for research purposes; commercial reactors, which are used to generate electricity; and gloveboxes, which supply transparent containment units in which hazardous materials are handled.
First is shutting down the site and removing operational waste. The second is to develop a decommissioning plan, including a schedule and budget, and get it approved and licensed by the U.S. Nuclear Regulatory Commission. The next step is to execute the plan in a strategic manner, then lastly, to assess the thoroughness of the process in accordance with the preapproved plan.
Many different considerations go into developing a decommissioning plan, including the amount and types of materials and waste that are on the site and the other contractors or specialists involved. The plan must also consider the procedures for removing and disposing materials on the site, which could require the licensee to provide workers with specialized training or deploy shielding or other equipment, such as remote or semi-remote systems.
“Depending on the risk level of the site, the process for regulatory approval could take months or several years to be fully completed, and thereafter allow the decommissioning work to start. It can take a couple years or even up to 10 years depending on the type of site you’re working on,” Boing said.
Once plans are approved, the licensee and contractors can begin working that plan – removing equipment in a pre-mediated process, moving towards the ‘hotter’ or more radioactive pieces, Boing said. When removing waste, workers must make sure that it is classified correctly and put into the correct configuration to be handled appropriately for shipping and ultimately disposal at a licensed off-site waste facility.
Finally, to assess whether a site has met agreed-upon standards for cleanup, contractors often rely on benchmarking tools like RESRAD. RESRAD, which refers to RESidual RADioactive materials, is a suite of software tools developed by the Environmental Science Division of Argonne National Laboratory. It has been used to derive cleanup criteria for hundreds of sites including the CP-5 reactor and other Argonne facilities.
Today RESRAD is widely used in more than 100 countries to evaluate radioactively contaminated sites and establish cleanup criteria. The tool calculates radiological dose and risk to humans, plants and animals through multiple pathways including direct exposure, inhalation of particulates and radon, and ingestion of plant foods, meat, milk, aquatic foods, water and soil.
“Without RESRAD it would be much harder to prove scientifically that a site is clean,” said researcher Charley Yu, the Argonne lead for the RESRAD program. “Other codes can calculate dose, but RESRAD is specifically developed to derive cleanup criteria for radiologically contaminated sites.”
Throughout the process, project management, waste management and stakeholder engagement are three key areas that the licensee must manage well to be successful, Boing said.
